Radially excited $\psi$ mesons and the $Y$ enhancements

Abstract

While many properties of the vector charmonium first excitations are yet to be measured, enhancements at unexpected energies are intriguing, alias the $Y$ states. In order to understand the naturally unquenched mesonic line-shapes, the influence of the most relevant hadronic decay channels must be taken into account. Within an unitary effective approach we present results where mesonic loops are included in an equivalent manner to coupled-channels. We show results for the $\psi(3770)$ and $\psi(4160)$ systems, where we find the nonperturbative effects of dynamical generation of poles and line-shape distortion.